The present invention relates to an interface switching technology which enables one apparatus connected to a network which has different interface specifications for a host and a device to function both as a host and a device.
As described at pages 240 to 249 of xe2x80x9cTransistor Technologyxe2x80x9d published in July 1997, interface modules for a host and a device differ from each other in specifications. This system will be described with reference to FIG. 6. FIG. 6 is a structural diagram of the prior art.
A host communication controller 601 is connected to a device communication controller 605 by data lines 602 and 603 of a network. A resistor 604 having a resistance value R1 is connected to the ground at one end and to the data lines 602 and 603 at the other end and a resistor 606 having a resistance value R2 is connected to a power source at one end and to the data line 602 at the other end.
When a device is not connected to the network, this can be confirmed from the fact that both the voltages of the data lines on a host side become a ground level. When a device is connected to the network, this can be automatically confirmed from the fact that the potential of the data line 602 which is determined by voltage division between R1 and R2 becomes larger than the ground level. When a device is not connected, the host communication controller 601 does not need to operate. When a device is connected, communication can be automatically carried out by detecting a change in the potential of the data line 602. Further, since the existence of a device is detected from the potential of the data line 602 in this network, it is possible to connect and disconnect the data lines while the power source is kept on.
In the conventional system, a system which serves both as a host and a device cannot be realized by a single connector due to the constitution of hardware. The conventional system only detects the existence of a device and cannot distinguish between a host and a device while a power source is kept on and switch its function.
It is an object of the present invention to provide an information processing apparatus which realizes a system for switching between a host and a device and a system for switching between a host and a device while a power source is kept on to enable an information apparatus such as a handy phone or portable terminal to serve as a host to control peripheral equipment at a time and as a device (modem in case of a handy phone) for another information processing apparatus at another time and to enable a device having the improved performance of a CPU to be used as a stand-alone information apparatus.
The information processing apparatus of the present invention makes possible communication by activating a selected controller with means of separating the data lines of a host communication controller and the data lines of a device communication controller and selecting the data lines of one of them and means for determining which is connected to a connector, a host or a device.